To measure the time to tree-initiation and the tree-growth rate, methods by visual measurements of trees in organic insulating materials through an ptical microscope have been used so far. We developed a system to measure tree-growth rate and degraded area of a tree in organic insulating materials using an optical microscope. It was, however, impossible to measure three-dimensional shape of a tree by those methods.
This paper describes the volume of a tree immediately after initiation, as well as changes in the configuration of the tree by a computerized tomography method and a light penetrating method.
Specimens were made of PMMA. As a result it was possible to record the cross sections of a tree by the method, and to describe the degraded volume of a tree from the sum total of the cross sections. We determined the specific characteristics of the degraded volume of tree and the cross section area of the tree. It was possible to recognize the difference of the shape of a tree by investigating characteristics.

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The electric field dependence of tan δ in oil-film composite insulating system sometimes hasa peak and then decreases, which is known as Garton effect. This phenomenon is associated with that under high voltage application carriers in oil can not contribute to the conduction loss all through a phase of applied electric field. Since the separation of the loss current from the extremely large capacitive current is usually very difficult, non-linear AC dissipation current waveform caused by Garton effect has not been measured.
The authors developed a new method for the measurement of high field AC dissipation current in polymeric insulating materials. We applied this technique to the detection of non-linear dissipation current and its waveform in oil-film composite insulating system associated with Garton effect. We measured the variation of dissipation current with applied field and its frequency.

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N₂ gas flow medium-vacuum arc plasma with titanium cathode is applied to the PVD process producing TiN films.
In this paper, plasma parameters of such arc are measured for the pressure range from 10^-3 to 10^-1 Torr using the optical emission spectroscopy and the probe technique. The experimental results show that the arc plasma contains Ti and N₂ as neutral particles, and Ti⁺, Ti⁺+ and N₂⁺ as ions. The spectral intensities of Ti⁺ and N₂ have maximum values at pressures of 2×10^-2 and 8×10^-3 Torr, respectively. As the pressure increases from 10^-3 to 10^-1 Torr, the electron energy decreases from 1.3 to 0.2eV and the electron density increases from 1.5×10¹⁰ to 1.5×10¹¹cm^-3.
As a result of analyzing the above characteristics using the corona model, it becomes evident that the pressure at which the number densities of Ti⁺ ion and N₂ molecule are maximum oincides with that at which TiN films are produced in the prevailing arc PVD apparatus.

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Electromagnetic interferances cause frequent troubles due to the fact that microelectronic circuits are operated at increasingly low level in those days. The design of electric devices must be made taking the electromagnetic compatibility into account. Simulation technique capable of solving the onhomogeneous field with unbounded electromagnetic radiation can be a great help for this. Helmholtz's equation for the axi-symmetric electromagnetic radiation problem is formulated by the finite element method incorporating with the hybrid-type infinite elements. Solution of a loop antenna is first given and consequently the numerical result shows a good agreement with the analytical one. Calculation is then extended to the shielding effects of conductive rings including their skin effect. It is shown that the shielding could be established if the equivalent conductivity of the conductors were higher than a certain level.

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Monte Carlo simulation (MCS) is applied to the estmation of illuminance distributions in infinitely long interiors which have visual obstructions and luminous surface ceilings. Although a number of lighting calculations by MCS have already been carried out in various interiors with point or linear light sources, such area sources as luminous surface ceilings and daylight through glass windows are rather common in many practical lighting designs.
So far illuminance distributions have scarcely been calculated taking into account the interreflection of luminous flux between wall surfaces in the interior space, particularly in the complicated lighting interiors which are partitioned by many visual obstructions and have an asymmetrical luminous surface ceiling.
The present paper compares illuminance distributions calculated by theoretical equations based on the contour integration method with those obtained by MCS in infinitely long concave interiors which have luminous surface ceilings of various shapes and four visual obstructions, and also describes the conservation law of photon bundles due to the interreflection between wall surfaces in these interior spaces.
As a result, it can be concluded that MCS results of direct illuminance distributions agree with those obtained by the contour integration method and that the conservation law of photon bundles in the concave interiors with transparent visual obstructions holds well. Therefore, it seems that MCS technique for illuminance calculation is a very powerful tool in infinitely long concave interior spaces

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It is found that the mean time lags of the breakdowns of an aluminum sphere gap in SF₆ gas enclosed in a test chamber are more decreased, when the chamber that has been exposed in a higher atmospheric humidity condition, prior to the gas filling, is used. The main purpose of the present paper is to investigate the cause of this phenomenon
It is confirmed in the present experiment that the water vapor content in the test chamber increases with the time elapsed after the gas filling. In the case that the time from a gas filling to a beginning of the time lag measurement is more increased, the increase in this water vapor causes the mean time lags to decrease markedly. This effect is considerable for the rough electrode, but a little for the smooth electrode. It is also found that the mean time lags is influenced by the condition of the cathode surface, not the anode. From these results, it is clear that the water vapor desorbed from the test chamber wall attaches to some microscopic protrusions on the cathode and accelerates the emission of the initiatory electrons, and then this results in the decrease in the mean time lags.

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We are planning to grow spherical Si single crystal in space by using space shuttle (SL-J) in 1991. The crystal growth will be done in a cylindrical electrical furnace in such a manner that the spherical Si melt with Si single crystal rod is solidified. The furnace temperature should be controlled so as to grow Si single crystal with proper solid-liquid interface.
The present study deals with the precision computer simulation of Si crystal growth in space. The crystal growth is influenced by various physical phenomena such as temperature conduction, natural and Marangoni convections, phase change and radiation from furnace. In the present treatment, a 2D-simulation with axial symmetry is carried out, taking into account of the 3D radiation field with a specific temperature distribution of the furnace wall.
The simulation program consists of four modules. The first module is used for the calculation of the parabolic partial differential equation by using the control volume method. The second one evaluates implicitly the phase change by the entalpy method. The third one is for computing the heat flux from surface by radiation. The last one is for calculating the view factors with Monte Carlo method, which are necessary to get the heat flux

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Following the preceding work, quantum mechanics for the photon is again investigated. First, the second-quantization of the free photon fields is carried out by means of the Lagrangian formalism. Operators of the momentum, of the Hamiltonian, and of the photon number of the system are obtained. Secondly, the interaction of first-quantized photon with the potential is investigated. Correspondence of our theory to the classical electromagnetic theory is also found.

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